Systems and methods for controlling a level of interference to a wireless receiver responsive to a power level associated with a wireless transmitter

ABSTRACT

A level of interference to a wireless receiver may be controlled by determining a set of frequencies to be assigned to a wireless transmitter, responsive to a power level associated with the wireless transmitter. The set of frequencies is then assigned to the wireless transmitter. Related systems, methods and devices are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/300,868,filed Dec. 15, 2005, entitled Aggregate Radiated Power Control forMulti-Band/Multi-Mode Satellite Radiotelephone Communications Systemsand Methods, which itself is a continuation of application Ser. No.10/819,542, filed Apr. 7, 2004, entitled Aggregate Radiated PowerControl for Multi-Band/Multi-Mode Satellite RadiotelephoneCommunications Systems and Methods, now U.S. Pat. No. 7,113,778, andwhich itself is a continuation-in-part (CIP) of application Ser. No.10/225,613, filed Aug. 22, 2002, entitled Multi-Band/Multi-ModeSatellite Radiotelephone Communications System and Methods, now U.S.Pat. No. 7,181,161, and is itself a continuation-in-part (CIP) ofapplication Ser. No. 10/074,097, filed Feb. 12, 2002, entitled Systemsand Methods for Terrestrial Reuse of Cellular Satellite FrequencySpectrum, now U.S. Pat. No. 6,684,057 all of which are assigned to theassignee of the present application, the disclosures of all of which arehereby incorporated herein by reference in their entirety as if setforth fully herein.

FIELD OF THE INVENTION

This invention relates to radiotelephone communications systems andmethods, and more particularly to terrestrial cellular and satellitecellular radiotelephone communications systems and methods.

BACKGROUND OF THE INVENTION

Satellite radiotelephone communications systems and methods are widelyused for radiotelephone communications. Satellite radiotelephonecommunications systems and methods generally employ at least onespace-based component, such as one or more satellites that areconfigured to wirelessly communicate with a plurality of satelliteradiotelephones.

A satellite radiotelephone communications system or method may utilize asingle antenna beam covering an entire area served by the system.Alternatively, in cellular satellite radiotelephone communicationssystems and methods, multiple beams are provided, each of which canserve distinct geographical areas in the overall service region, tocollectively serve an overall satellite footprint. Thus, a cellulararchitecture similar to that used in conventional terrestrial cellularradiotelephone systems and methods can be implemented in cellularsatellite-based systems and methods. The satellite typicallycommunicates with radiotelephones over a bidirectional communicationspathway, with radiotelephone communication signals being communicatedfrom the satellite to the radiotelephone over a downlink or forwardlink, and from the radiotelephone to the satellite over an uplink orreturn link.

The overall design and operation of cellular satellite radiotelephonesystems and methods are well known to those having skill in the art, andneed not be described further herein. Moreover, as used herein, the term“radiotelephone” includes cellular and/or satellite radiotelephones withor without a multi-line display; Personal Communications System (PCS)terminals that may combine a radiotelephone with data processing,facsimile and/or data communications capabilities; Personal DigitalAssistants (PDA) that can include a radio frequency transceiver and apager, Internet/intranet access, Web browser, organizer, calendar and/ora global positioning system (GPS) receiver; and/or conventional laptopand/or palmtop computers or other appliances, which include a radiofrequency transceiver. A radiotelephone also may be referred to hereinas a radioterminal.

Terrestrial networks can enhance cellular satellite radiotelephonesystem availability, efficiency and/or economic viability byterrestrially reusing at least some of the frequency bands that areallocated to cellular satellite radiotelephone systems. In particular,it is known that it may be difficult for cellular satelliteradiotelephone systems to reliably serve densely populated areas,because the satellite signal may be blocked by high-rise structuresand/or may not penetrate into buildings. As a result, the satellitespectrum may be underutilized or unutilized in such areas. Theterrestrial reuse of at least some of a satellite band's frequencies canreduce or eliminate this potential problem.

Moreover, the capacity of the overall system can be increasedsignificantly by the introduction of terrestrial reuse of a satelliteband's frequencies, since terrestrial frequency reuse can be much denserthan that of a satellite-only system. In fact, capacity can be enhancedwhere it may be mostly needed, i.e., densely populatedurban/industrial/commercial areas. As a result, the overall system canbecome much more economically viable, as it may be able to serve a muchlarger subscriber base.

One example of terrestrial reuse of satellite frequencies is describedin U.S. Pat. No. 5,937,332 to the present inventor Karabinis entitledSatellite Telecommunications Repeaters and Retransmission Methods, thedisclosure of which is hereby incorporated herein by reference in itsentirety as if set forth fully herein. As described therein, satellitetelecommunications repeaters are provided which receive, amplify, andlocally retransmit the downlink signal received from a satellite therebyincreasing the effective downlink margin in the vicinity of thesatellite telecommunications repeaters and allowing an increase in thepenetration of uplink and downlink signals into buildings, foliage,transportation vehicles, and other objects which can reduce link margin.Both portable and non-portable repeaters are provided. See the abstractof U.S. Pat. No. 5,937,332.

Finally, satellite radiotelephones for a satellite radiotelephone systemor method having a terrestrial component within the same satellitefrequency band and using substantially the same air interface for bothterrestrial and satellite communications can be cost effective and/oraesthetically appealing. Conventional dual band/dual mode alternatives,such as the well known Thuraya, Iridium and/or Globalstar dual modesatellite/terrestrial radiotelephone systems, may duplicate somecomponents, which may lead to increased cost, size and/or weight of theradiotelephone. See U.S. Pat. No. 6,052,560 to the present inventorKarabinis, entitled Satellite System Utilizing a Plurality of AirInterface Standards and Method Employing Same.

In view of the above discussion, there continues to be a need forsystems and methods for terrestrial reuse of cellular satellitefrequencies that can allow improved reliability, capacity, costeffectiveness and/or aesthetic appeal for cellular satelliteradiotelephone systems, methods and/or satellite radiotelephones.

SUMMARY OF THE INVENTION

A level of interference to a wireless receiver may be controlled,according to some embodiments of the present invention, by determining aset of frequencies to be assigned to a wireless transmitter, responsiveto a power level associated with the wireless transmitter. The set offrequencies is then assigned to the wireless transmitter.

In some embodiments, a frequency distance between the set of frequenciesand a band of frequencies used for reception by the wireless receiver isincreased, and in some embodiments monotonically increased, as the powerlevel increases. In other embodiments, a frequency distance between theset of frequencies and the band of frequencies used for reception by thewireless receiver is decreased, and in some embodiments monotonicallydecreased, as the power level decreases.

In some embodiments, the set of frequencies is included in a satellitefrequency band. Moreover, in some embodiments, the wireless receiver isa wireless transceiver and determining a set of frequencies is furtherresponsive to a detection of a signal from the wireless transceiver. Thedetection may be performed by a base station serving the wirelesstransmitter. In other embodiments, the determining of the set offrequencies may be responsive to a geographic location of the wirelesstransmitter.

Embodiments of the invention have been described above primarily interms of methods of controlling the level of interference to a wirelessreceiver. However, other embodiments provide analogous systems forcontrolling a level of interference to a wireless receiver. Thesesystems may include a controller that is configured to determine a setof frequencies to be assigned to a wireless transmitter responsive to apower level associated with the wireless transmitter, according to anyof the above-described embodiments. Moreover, still other embodiments ofthe present invention provide a wireless transmitter itself, that usesthe set of frequencies that is assigned thereto responsive to a powerlevel associated with the wireless transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of cellular radiotelephone systems andmethods according to embodiments of the invention.

FIG. 2 is a block diagram of adaptive interference reducers according toembodiments of the present invention.

FIG. 3 is a spectrum diagram that illustrates satellite L-band frequencyallocations.

FIG. 4 is a schematic diagram of cellular satellite systems and methodsaccording to other embodiments of the present invention.

FIG. 5 illustrates time division duplex frame structures according toembodiments of the present invention.

FIG. 6 is a block diagram of architectures of ancillary terrestrialcomponents according to embodiments of the invention.

FIG. 7 is a block diagram of architectures of reconfigurableradiotelephones according to embodiments of the invention.

FIG. 8 graphically illustrates mapping of monotonically decreasing powerlevels to frequencies according to embodiments of the present invention.

FIG. 9 illustrates an ideal cell that is mapped to three power regionsand three associated carrier frequencies according to embodiments of theinvention.

FIG. 10 depicts a realistic cell that is mapped to three power regionsand three associated carrier frequencies according to embodiments of theinvention.

FIG. 11 illustrates two or more contiguous slots in a frame that areunoccupied according to embodiments of the present invention.

FIG. 12 illustrates loading of two or more contiguous slots with lowerpower transmissions according to embodiments of the present invention.

FIG. 13 is a block diagram of satellite radiotelephone systems andmethods according to some embodiments of the invention.

FIG. 14 is a schematic diagram of terrestrial frequency reuse ofsatellite frequencies according to some embodiments of the invention.

FIG. 15 is a block diagram of radiotelephones according to someembodiments of the invention.

FIG. 16 is a schematic diagram of satellite radiotelephone systems andmethods according to some embodiments of the invention.

FIG. 17 is a schematic diagram of satellite radiotelephone systems andmethods according to some embodiments of the invention.

FIG. 18 is a schematic diagram of satellite radiotelephone systems andmethods including aggregate radiated power control according to someembodiments of the present invention.

FIG. 19 is a schematic diagram of an ancillary terrestrial networkincluding systems and methods that can increase link margins accordingto some embodiments of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. However, this invention should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. Like numbers refer to like elements throughout.

FIG. 1 is a schematic diagram of cellular satellite radiotelephonesystems and methods according to embodiments of the invention. As shownin FIG. 1, these cellular satellite radiotelephone systems and methods100 include at least one Space-Based Component (SBC) 110, such as asatellite. The space-based component 110 is configured to transmitwireless communications to a plurality of radiotelephones 120 a, 120 bin a satellite footprint comprising one or more satellite radiotelephonecells 130-130″″ over one or more satellite radiotelephone forward link(downlink) frequencies f_(D). The space-based component 110 isconfigured to receive wireless communications from, for example, a firstradiotelephone 120 a in the satellite radiotelephone cell 130 over asatellite radiotelephone return link (uplink) frequency f_(U). Anancillary terrestrial network, comprising at least one ancillaryterrestrial component 140, which may include an antenna 140 a and anelectronics system 140 b (for example, at least one antenna 140 a and atleast one electronics system 140 b), is configured to receive wirelesscommunications from, for example, a second radiotelephone 120 b in theradiotelephone cell 130 over the satellite radiotelephone uplinkfrequency, denoted f′_(U), which may be the same as f_(U). Thus, asillustrated in FIG. 1, radiotelephone 120 a may be communicating withthe space-based component 110 while radiotelephone 120 b may becommunicating with the ancillary terrestrial component 140. As shown inFIG. 1, the space-based component 110 also undesirably receives thewireless communications from the second radiotelephone 120 b in thesatellite radiotelephone cell 130 over the satellite radiotelephonefrequency f′_(U) as interference. More specifically, a potentialinterference path is shown at 150. In this potential interference path150, the return link signal of the second radiotelephone 120 b atcarrier frequency f′_(U) interferes with satellite communications. Thisinterference would generally be strongest when f′_(U)=f_(U), because, inthat case, the same return link frequency would be used for space-basedcomponent and ancillary terrestrial component communications over thesame satellite radiotelephone cell, and no spatial discriminationbetween satellite radiotelephone cells would appear to exist.

Still referring to FIG. 1, embodiments of satellite radiotelephonesystems/methods 100 can include at least one gateway 160 that caninclude an antenna 160 a and an electronics system 160 b that can beconnected to other networks 162 including terrestrial and/or otherradiotelephone networks. The gateway 160 also communicates with thespace-based component 110 over a satellite feeder link 112. The gateway160 also communicates with the ancillary terrestrial component 140,generally over a terrestrial link 142.

Still referring to FIG. 1, an Interference Reducer (IR) 170 a also maybe provided at least partially in the ancillary terrestrial componentelectronics system 140 b. Alternatively or additionally, an interferencereducer 170 b may be provided at least partially in the gatewayelectronics system 160 b. In yet other alternatives, the interferencereducer may be provided at least partially in other components of thecellular satellite system/method 100 instead of or in addition to theinterference reducer 170 a and/or 170 b. The interference reducer isresponsive to the space-based component 110 and to the ancillaryterrestrial component 140, and is configured to reduce the interferencefrom the wireless communications that are received by the space-basedcomponent 110 and is at least partially generated by the secondradiotelephone 120 b in the satellite radiotelephone cell 130 over thesatellite radiotelephone frequency f′_(U). The interference reducer 170a and/or 170 b uses the wireless communications f′_(U) that are intendedfor the ancillary terrestrial component 140 from the secondradiotelephone 120 b in the satellite radiotelephone cell 130 using thesatellite radiotelephone frequency f′_(U) to communicate with theancillary terrestrial component 140.

In embodiments of the invention, as shown in FIG. 1, the ancillaryterrestrial component 140 generally is closer to the first and secondradiotelephones 120 a and 120 b, respectively, than is the space-basedcomponent 110, such that the wireless communications from the secondradiotelephone 120 b are received by the ancillary terrestrial component140 prior to being received by the space-based component 110. Theinterference reducer 170 a and/or 170 b is configured to generate aninterference cancellation signal comprising, for example, at least onedelayed replica of the wireless communications from the secondradiotelephone 120 b that are received by the ancillary terrestrialcomponent 140, and to subtract the delayed replica of the wirelesscommunications from the second radiotelephone 120 b that are received bythe ancillary terrestrial component 140 from the wireless communicationsthat are received from the space-based component 110. The interferencereduction signal may be transmitted from the ancillary terrestrialcomponent 140 to the gateway 160 over link 142 and/or using otherconventional techniques.

Thus, adaptive interference reduction techniques may be used to at leastpartially cancel the interfering signal, so that the same, or othernearby, satellite radiotelephone uplink frequency can be used in a givencell for communications by radiotelephones 120 with the satellite 110and with the ancillary terrestrial component 140. Accordingly, allfrequencies that are assigned to a given cell 130 may be used for bothradiotelephone 120 communications with the space-based component 110 andwith the ancillary terrestrial component 140. Conventional systems mayavoid terrestrial reuse of frequencies within a given satellite cellthat are being used within the satellite cell for satellitecommunications. Stated differently, conventionally, only frequenciesused by other satellite cells may be candidates for terrestrial reusewithin a given satellite cell. Beam-to-beam spatial isolation that isprovided by the satellite system was relied upon to reduce or minimizethe level of interference from the terrestrial operations into thesatellite operations. In sharp contrast, embodiments of the inventioncan use an interference reducer to allow all frequencies assigned to asatellite cell to be used terrestrially and for satellite radiotelephonecommunications.

Embodiments of the invention according to FIG. 1 may arise from arealization that the return link signal from the second radiotelephone120 b at f′_(U) generally will be received and processed by theancillary terrestrial component 140 much earlier relative to the timewhen it will arrive at the satellite gateway 160 from the space-basedcomponent 110 via the interference path 150. Accordingly, theinterference signal at the satellite gateway 160 b can be at leastpartially canceled. Thus, as shown in FIG. 1, an interferencecancellation signal, such as the demodulated ancillary terrestrialcomponent signal, can be sent to the satellite gateway 160 b by theinterference reducer 170 a in the ancillary terrestrial component 140,for example using link 142. In the interference reducer 170 b at thegateway 160 b, a weighted (in amplitude and/or phase) replica of thesignal may be formed using, for example, adaptive transversal filtertechniques that are well known to those having skill in the art. Then, atransversal filter output signal is subtracted from the aggregatereceived satellite signal at frequency f′_(U) that contains desired aswell as interference signals. Thus, the interference cancellation neednot degrade the signal-to-noise ratio of the desired signal at thegateway 160, because a regenerated (noise-free) terrestrial signal, forexample as regenerated by the ancillary terrestrial component 140, canbe used to perform interference suppression.

FIG. 2 is a block diagram of embodiments of adaptive interferencecancellers that may be located in the ancillary terrestrial component140, in the gateway 160, and/or in another component of the cellularradiotelephone system 100. As shown in FIG. 2, one or more controlalgorithms 204, known to those having skill in the art, may be used toadaptively adjust the coefficients of a plurality of transversal filters202 a-202 n. Adaptive algorithms, such as Least Mean Square Error(LMSE), Kalman, Fast Kalman, Zero Forcing and/or various combinationsthereof or other techniques may be used. It will be understood by thosehaving skill in the art that the architecture of FIG. 2 may be used withan LMSE algorithm. However, it also will be understood by those havingskill in the art that conventional architectural modifications may bemade to facilitate other control algorithms.

Additional embodiments of the invention now will be described withreference to FIG. 3, which illustrates L-band frequency allocationsincluding cellular radiotelephone system forward links and return links.As shown in FIG. 3, the space-to-ground L-band forward link (downlink)frequencies are assigned from 1525 MHz to 1559 MHz. The ground-to-spaceL-band return link (uplink) frequencies occupy the band from 1626.5 MHzto 1660.5 MHz. Between the forward and return L-band links lie theGPS/GLONASS radionavigation band (from 1559 MHz to 1605 MHz).

In the detailed description to follow, GPS/GLONASS will be referred tosimply as GPS for the sake of brevity. Moreover, the acronyms ATC andSBC will be used for the ancillary terrestrial component and thespace-based component, respectively, for the sake of brevity.

As is known to those skilled in the art, GPS receivers may be extremelysensitive since they are designed to operate on very weakspread-spectrum radionavigation signals that arrive on the earth from aGPS satellite constellation. As a result, GPS receivers may to be highlysusceptible to in-band interference. ATCs that are configured to radiateL-band frequencies in the forward satellite band (1525 to 1559 MHz) canbe designed with very sharp out-of-band emissions filters to satisfy thestringent out-of-band spurious emissions desires of GPS.

Referring again to FIG. 1, some embodiments of the invention can providesystems and methods that can allow an ATC 140 to configure itself in oneof at least two modes. In accordance with a first mode, which may be astandard mode and may provide highest capacity, the ATC 140 transmits tothe radiotelephones 120 over the frequency range from 1525 MHz to 1559MHz, and receives transmissions from the radiotelephones 120 in thefrequency range from 1626.5 MHz to 1660.5 MHz, as illustrated in FIG. 3.In contrast, in a second mode of operation, the ATC 140 transmitswireless communications to the radiotelephones 120 over a modified rangeof satellite band forward link (downlink) frequencies. The modifiedrange of satellite band forward link frequencies may be selected toreduce, compared to the unmodified range of satellite band forward linkfrequencies, interference with wireless receivers such as GPS receiversthat operate outside the range of satellite band forward linkfrequencies.

Many modified ranges of satellite band forward link frequencies may beprovided according to embodiments of the present invention. In someembodiments, the modified range of satellite band forward linkfrequencies can be limited to a subset of the original range ofsatellite band forward link frequencies, so as to provide a guard bandof unused satellite band forward link frequencies. In other embodiments,all of the satellite band forward link frequencies are used, but thewireless communications to the radiotelephones are modified in a mannerto reduce interference with wireless receivers that operate outside therange of satellite band forward link frequencies. Combinations andsubcombinations of these and/or other techniques also may be used, aswill be described below.

It also will be understood that embodiments of the invention that willnow be described in connection with FIGS. 4-12 will be described interms of multiple mode ATCs 140 that can operate in a first standardmode using the standard forward and return links of FIG. 3, and in asecond or alternate mode that uses a modified range of satellite bandforward link frequencies and/or a modified range of satellite bandreturn link frequencies. These multiple mode ATCs can operate in thesecond, non-standard mode, as long as desirable, and can be switched tostandard mode otherwise. However, other embodiments of the presentinvention need not provide multiple mode ATCs but, rather, can provideATCs that operate using the modified range of satellite band forwardlink and/or return link frequencies.

Embodiments of the invention now will be described, wherein an ATCoperates with an SBC that is configured to receive wirelesscommunications from radiotelephones over a first range of satellite bandreturn link frequencies and to transmit wireless communications to theradiotelephones over a second range of satellite band forward linkfrequencies that is spaced apart from the first range. According tothese embodiments, the ATC is configured to use at least one timedivision duplex frequency to transmit wireless communications to theradiotelephones and to receive wireless communications from theradiotelephones at different times. In particular, in some embodiments,the at least one time division duplex frequency that is used to transmitwireless communications to the radiotelephones and to receive wirelesscommunications from the radiotelephones at different times, comprises aframe including a plurality of slots. At least a first one of the slotsis used to transmit wireless communications to the radiotelephones andat least a second one of the slots is used to receive wirelesscommunications from the radiotelephones. Thus, in some embodiments, theATC transmits and receives, in Time Division Duplex (TDD) mode, usingfrequencies from 1626.5 MHz to 1660.5 MHz. In some embodiments, all ATCsacross the entire network may have the statedconfiguration/reconfiguration flexibility. In other embodiments, onlysome ATCs may be reconfigurable.

FIG. 4 illustrates satellite systems and methods 400 according to someembodiments of the invention, including an ATC 140 communicating with aradiotelephone 120 b using a carrier frequency f″_(U) in TDD mode. FIG.5 illustrates an embodiment of a TDD frame structure. Assuming full-rateGSM (eight time slots per frame), up to four full-duplex voice circuitscan be supported by one TDD carrier. As shown in FIG. 5, the ATC 140transmits to the radiotelephone 120 b over, for example, time slotnumber 0. The radiotelephone 120 b receives and replies back to the ATC140 over, for example, time slot number 4. Time slots number 1 and 5 maybe used to establish communications with another radiotelephone, and soon.

A Broadcast Control CHannel (BCCH) is preferably transmitted from theATC 140 in standard mode, using a carrier frequency from below any guardband exclusion region. In other embodiments, a BCCH also can be definedusing a TDD carrier. In any of these embodiments, radiotelephones inidle mode can, per established GSM methodology, monitor the BCCH andreceive system-level and paging information. When a radiotelephone ispaged, the system decides what type of resource to allocate to theradiotelephone in order to establish the communications link. Whatevertype of resource is allocated for the radiotelephone communicationschannel (TDD mode or standard mode), the information is communicated tothe radiotelephone, for example as part of the call initializationroutine, and the radiotelephone configures itself appropriately.

It may be difficult for the TDD mode to co-exist with the standard modeover the same ATC, due, for example, to the ATC receiver LNA stage. Inparticular, assuming a mixture of standard and TDD mode GSM carriersover the same ATC, during the part of the frame when the TDD carriersare used to serve the forward link (when the ATC is transmitting TDD)enough energy may leak into the receiver front end of the same ATC todesensitize its LNA stage.

Techniques can be used to suppress the transmitted ATC energy over the1600 MHz portion of the band from desensitizing the ATC's receiver LNA,and thereby allow mixed standard mode and TDD frames. For example,isolation between outbound and inbound ATC front ends and/or antennasystem return loss may be increased or maximized. A switchableband-reject filter may be placed in front of the LNA stage. This filterwould be switched in the receiver chain (prior to the LNA) during thepart of the frame when the ATC is transmitting TDD, and switched outduring the rest of the time. An adaptive interference canceller can beconfigured at RF (prior to the LNA stage). If such techniques are used,suppression of the order of 70 dB can be attained, which may allow mixedstandard mode and TDD frames. However, the ATC complexity and/or costmay increase.

Thus, even though ATC LNA desensitization may be reduced or eliminated,it may use significant special engineering and attention and may not beeconomically worth the effort. Other embodiments, therefore, may keepTDD ATCs pure TDD, with the exception, perhaps, of the BCCH carrierwhich may not be used for traffic but only for broadcasting over thefirst part of the frame, consistent with TDD protocol. Moreover, RandomAccess CHannel (RACH) bursts may be timed so that they arrive at the ATCduring the second half of the TDD frame. In some embodiments, all TDDATCs may be equipped to enable reconfiguration in response to a command.

It is well recognized that during data communications or otherapplications, the forward link may use transmissions at higher ratesthan the return link. For example, in web browsing with aradiotelephone, mouse clicks and/or other user selections typically aretransmitted from the radiotelephone to the system. The system, however,in response to a user selection, may have to send large data files tothe radiotelephone. Hence, other embodiments of the invention may beconfigured to enable use of an increased or maximum number of time slotsper forward GSM carrier frame, to provide a higher downlink data rate tothe radiotelephones.

Thus, when a carrier frequency is configured to provide service in TDDmode, a decision may be made as to how many slots will be allocated toserving the forward link, and how many will be dedicated to the returnlink. Whatever the decision is, it may be desirable that it be adheredto by all TDD carriers used by the ATC, in order to reduce or avoid theLNA desensitization problem described earlier. In voice communications,the partition between forward and return link slots may be made in themiddle of the frame as voice activity typically is statisticallybidirectionally symmetrical. Hence, driven by voice, the center of theframe may be where the TDD partition is drawn.

To increase or maximize forward link throughput in data mode, data modeTDD carriers according to embodiments of the invention may use a morespectrally efficient modulation and/or protocol, such as the EDGEmodulation and/or protocol, on the forward link slots. The return linkslots may be based on a less spectrally efficient modulation and/orprotocol such as the GPRS (GMSK) modulation and/or protocol. The EDGEmodulation/protocol and the GPRS modulation/protocol are well known tothose having skill in the art, and need not be described further herein.Given an EDGE forward/GPRS return TDD carrier strategy, up to(384/2)=192 kbps may be supported on the forward link while on thereturn link the radiotelephone may transmit at up to (115/2)≈64 kbps.

In other embodiments, it also is possible to allocate six time slots ofan eight-slot frame for the forward link and only two for the returnlink. In these embodiments, for voice services, given the statisticallysymmetric nature of voice, the return link vocoder may need to becomparable with quarter-rate GSM, while the forward link vocoder canoperate at full-rate GSM, to yield six full-duplex voice circuits perGSM TDD-mode carrier (a voice capacity penalty of 25%). Subject to thisnon-symmetrical partitioning strategy, data rates of up to(384)(6/8)=288 kbps may be achieved on the forward link, with up to(115)(2/8) 32 kbps on the return link.

FIG. 6 depicts an ATC architecture according to embodiments of theinvention, which can lend itself to automatic configuration between thetwo modes of standard GSM and TDD GSM on command, for example, from aNetwork Operations Center (NOC) via a Base Station Controller (BSC). Itwill be understood that in these embodiments, an antenna 620 cancorrespond to the antenna 140 a of FIGS. 1 and 4, and the remainder ofFIG. 6 can correspond to the electronics system 140 b of FIGS. 1 and 4.If a reconfiguration command for a particular carrier, or set ofcarriers, occurs while the carrier(s) are active and are supportingtraffic, then, via the in-band signaling Fast Associated Control CHannel(FACCH), all affected radiotelephones may be notified to alsoreconfigure themselves and/or switch over to new resources. Ifcarrier(s) are reconfigured from TDD mode to standard mode, automaticreassignment of the carrier(s) to the appropriate standard-mode ATCs,based, for example, on capacity demand and/or reuse pattern can beinitiated by the NOC. If, on the other hand, carrier(s) are reconfiguredfrom standard mode to TDD mode, automatic reassignment to theappropriate TDD-mode ATCs can take place on command from the NOC.

Still referring to FIG. 6, a switch 610 may remain closed when carriersare to be demodulated in the standard mode. In TDD mode, this switch 610may be open during the first half of the frame, when the ATC istransmitting, and closed during the second half of the frame, when theATC is receiving. Other embodiments also may be provided.

FIG. 6 assumes N transceivers per ATC sector, where N can be as small asone, since a minimum of one carrier per sector generally is desired.Each transceiver is assumed to operate over one GSM carrier pair (whenin standard mode) and can thus support up to eight full-duplex voicecircuits, neglecting BCCH channel overhead. Moreover, a standard GSMcarrier pair can support sixteen full-duplex voice circuits when inhalf-rate GSM mode, and up to thirty two full-duplex voice circuits whenin quarter-rate GSM mode.

When in TDD mode, the number of full duplex voice circuits may bereduced by a factor of two, assuming the same vocoder. However, in TDDmode, voice service can be offered via the half-rate GSM vocoder withalmost imperceptible quality degradation, in order to maintain invariantvoice capacity. FIG. 7 is a block diagram of a reconfigurableradiotelephone architecture that can communicate with a reconfigurableATC architecture of FIG. 6. In FIG. 7, an antenna 720 is provided, andthe remainder of FIG. 7 can provide embodiments of an electronics systemfor the radiotelephone.

It will be understood that the ability to reconfigure ATCs andradiotelephones according to embodiments of the invention may beobtained at a relatively small increase in cost. The cost may be mostlyin Non-Recurring Engineering (NRE) cost to develop software. Somerecurring cost may also be incurred, however, in that at least anadditional RF filter and a few electronically controlled switches may beused per ATC and radiotelephone. All other hardware/software can becommon to standard-mode and TDD-mode GSM.

Referring now to FIG. 8, other radiotelephone systems and methodsaccording to embodiments of the invention now will be described. Inthese embodiments, the modified second range of satellite band forwardlink frequencies includes a plurality of frequencies in the second rangeof satellite band forward link frequencies that are transmitted by theATCs to the radiotelephones at a power level, such as maximum powerlevel, that monotonically decreases as a function of (increasing)frequency. More specifically, as will be described below, in someembodiments, the modified second range of satellite band forward linkfrequencies includes a subset of frequencies proximate to a first orsecond end of the range of satellite band forward link frequencies thatare transmitted by the ATC to the radiotelephones at a power level, suchas a maximum power level, that monotonically decreases toward the firstor second end of the second range of satellite band forward linkfrequencies. In still other embodiments, the first range of satelliteband return link frequencies is contained in an L-band of satellitefrequencies above GPS frequencies and the second range of satellite bandforward link frequencies is contained in the L-band of satellitefrequencies below the GPS frequencies. The modified second range ofsatellite band forward link frequencies includes a subset of frequenciesproximate to an end of the second range of satellite band forward linkfrequencies adjacent the GPS frequencies that are transmitted by the ATCto the radiotelephones at a power level, such as a maximum power level,that monotonically decreases toward the end of the second range ofsatellite band forward link frequencies adjacent the GPS frequencies.

Without being bound by any theory of operation, a theoretical discussionof the mapping of ATC maximum power levels to carrier frequenciesaccording to embodiments of the present invention now will be described.Referring to FIG. 8, let ν=

(ρ) represent a mapping from the power (ρ) domain to the frequency (ν)range. The power (ρ) is the power that an ATC uses or should transmit inorder to reliably communicate with a given radiotelephone. This powermay depend on many factors such as the radiotelephone's distance fromthe ATC, the blockage between the radiotelephone and the ATC, the levelof multipath fading in the channel, etc., and as a result, will, ingeneral, change as a function of time. Hence, the power used generallyis determined adaptively (iteratively) via closed-loop power control,between the radiotelephone and ATC.

The frequency (ν) is the satellite carrier frequency that the ATC usesto communicate with the radiotelephone. According to embodiments of theinvention, the mapping

is a monotonically decreasing function of the independent variable ρ.Consequently, in some embodiments, as the maximum ATC power increases,the carrier frequency that the ATC uses to establish and/or maintain thecommunications link decreases. FIG. 8 illustrates an embodiment of apiece-wise continuous monotonically decreasing (stair-case) function.Other monotonic functions may be used, including linear and/ornonlinear, constant and/or variable decreases. FACCH or Slow AssociatedControl CHannel (SACCH) messaging may be used in embodiments of theinvention to facilitate the mapping adaptively and in substantially realtime.

FIG. 9 depicts an ideal cell according to embodiments of the invention,where, for illustration purposes, three power regions and threeassociated carrier frequencies (or carrier frequency sets) are beingused to partition a cell. For simplicity, one ATC transmitter at thecenter of the idealized cell is assumed with no sectorization. Inembodiments of FIG. 9, the frequency (or frequency set) f_(I) is takenfrom substantially the upper-most portion of the L-band forward linkfrequency set, for example from substantially close to 1559 MHz (seeFIG. 3). Correspondingly, the frequency (or frequency set) f_(M) istaken from substantially the central portion of the L-band forward linkfrequency set (see FIG. 3). In concert with the above, the frequency (orfrequency set) f_(O) is taken from substantially the lowest portion ofthe L-band forward link frequencies, for example close to 1525 MHz (seeFIG. 3).

Thus, according to embodiments of FIG. 9, if a radiotelephone is beingserved within the outer-most ring of the cell, that radiotelephone isbeing served via frequency f_(O). This radiotelephone, being within thefurthest area from the ATC, has (presumably) requested maximum (or nearmaximum) power output from the ATC. In response to the maximum (or nearmaximum) output power request, the ATC uses its a priori knowledge ofpower-to-frequency mapping, such as a three-step staircase function ofFIG. 9. Thus, the ATC serves the radiotelephone with a low-valuefrequency taken from the lowest portion of the mobile L-band forwardlink frequency set, for example, from as close to 1525 MHz as possible.This, then, can provide additional safeguard to any GPS receiver unitthat may be in the vicinity of the ATC.

Embodiments of FIG. 9 may be regarded as idealized because theyassociate concentric ring areas with carrier frequencies (or carrierfrequency sets) used by an ATC to serve its area. In reality, concentricring areas generally will not be the case. For example, a radiotelephonecan be close to the ATC that is serving it, but with significantblockage between the radiotelephone and the ATC due to a building. Thisradiotelephone, even though relatively close to the ATC, may alsorequest maximum (or near maximum) output power from the ATC. With thisin mind, FIG. 10 may depict a more realistic set of area contours thatmay be associated with the frequencies being used by the ATC to serveits territory, according to embodiments of the invention. The frequency(or frequency set) f_(I) may be reused in the immediately adjacent ATCcells owing to the limited geographical span associated with f_(I)relative to the distance between cell centers. This may also hold forf_(M).

Referring now to FIG. 11, other modified second ranges of satellite bandforward link frequencies that can be used by ATCs according toembodiments of the present invention now will be described. In theseembodiments, at least one frequency in the modified second range ofsatellite band forward link frequencies that is transmitted by the ATCto the radiotelephones comprises a frame including a plurality of slots.In these embodiments, at least two contiguous slots in the frame that istransmitted by the ATC to the radiotelephones are left unoccupied. Inother embodiments, three contiguous slots in the frame that istransmitted by the ATC to the radiotelephones are left unoccupied. Inyet other embodiments, at least two contiguous slots in the frame thatis transmitted by the ATC to the radiotelephones are transmitted atlower power than remaining slots in the frame. In still otherembodiments, three contiguous slots in the frame that is transmitted bythe ATC to the radiotelephones are transmitted at lower power thanremaining slots in the frame. In yet other embodiments, the lower powerslots may be used with first selected ones of the radiotelephones thatare relatively close to the ATC and/or are experiencing relatively smallsignal blockage, and the remaining slots are transmitted at higher powerto second selected ones of the radiotelephones that are relatively farfrom the ATC and/or are experiencing relatively high signal blockage.

Stated differently, in accordance with some embodiments of theinvention, only a portion of the TDMA frame is utilized. For example,only the first four (or last four, or any contiguous four) time slots ofa full-rate GSM frame are used to support traffic. The remaining slotsare left unoccupied (empty). In these embodiments, capacity may be lost.However, as has been described previously, for voice services, half-rateand even quarter-rate GSM may be invoked to gain capacity back, withsome potential degradation in voice quality. The slots that are notutilized preferably are contiguous, such as slots 0 through 3 or 4through 7 (or 2 through 5, etc.). The use of non-contiguous slots suchas 0, 2, 4, and 6, for example, may be less desirable. FIG. 11illustrates four slots (4-7) being used and four contiguous slots (0-3)being empty in a GSM frame.

It has been found experimentally, according to these embodiments of theinvention, that GPS receivers can perform significantly better when theinterval between interference bursts is increased or maximized. Withoutbeing bound by any theory of operation, this effect may be due to therelationship between the code repetition period of the GPS C/A code (1msec.) and the GSM burst duration (about 0.577 msec.). With a GSM frameoccupancy comprising alternate slots, each GPS signal code period canexperience at least one “hit”, whereas a GSM frame occupancy comprisingfour to five contiguous slots allows the GPS receiver to derivesufficient clean information, so as to “flywheel” through the errorevents.

According to other embodiments of the invention, embodiments of FIGS.8-10 can be combined with embodiments of FIG. 11. Furthermore, accordingto other embodiments of the invention, if an f_(I) carrier of FIG. 9 or10 is underutilized, because of the relatively small footprint of theinner-most region of the cell, it may be used to support additionaltraffic over the much larger outermost region of the cell.

Thus, for example, assume that only the first four slots in each frameof f_(I) are being used for inner region traffic. In embodiments ofFIGS. 8-10, these four f_(I) slots are carrying relatively low powerbursts, for example of the order of 100 mW or less, and may, therefore,appear as (almost) unoccupied from an interference point of view.Loading the remaining four (contiguous) time slots of f_(I) withrelatively high-power bursts may have negligible effect on a GPSreceiver because the GPS receiver would continue to operate reliablybased on the benign contiguous time interval occupied by the fourlow-power GSM bursts. FIG. 12 illustrates embodiments of a frame atcarrier f_(I) supporting four low-power (inner interval) users and fourhigh-power (outer interval) users. In fact, embodiments illustrated inFIG. 12 may be a preferred strategy for the set of available carrierfrequencies that are closest to the GPS band. These embodiments mayavoid undue capacity loss by more fully loading the carrier frequencies.

The experimental finding that interference from GSM carriers can berelatively benign to GPS receivers provided that no more than, forexample, 5 slots per 8 slot GSM frame are used in a contiguous fashioncan be very useful. It can be particularly useful since thisexperimental finding may hold even when the GSM carrier frequency isbrought very close to the GPS band (as close as 1558.5 MHz) and thepower level is set relatively high. For example, with five contiguoustime slots per frame populated, the worst-case measured GPS receiver mayattain at least 30 dB of desensitization margin, over the entire ATCservice area, even when the ATC is radiating at 1558.5 MHz. With fourcontiguous time slots per frame populated, an additional 10 dBdesensitization margin may be gained for a total of 40 dB for theworst-case measured GPS receiver, even when the ATC is radiating at1558.5 MHz.

There still may be concern about the potential loss in network capacity(especially in data mode) that may be incurred over the frequencyinterval where embodiments of FIG. 111 are used to underpopulate theframe. Moreover, even though embodiments of FIG. 12 can avoid capacityloss by fully loading the carrier, they may do so subject to theconstraint of filling up the frame with both low-power and high-powerusers. Moreover, if forward link carriers are limited to 5 contiguoushigh power slots per frame, the maximum forward link data rate percarrier that may be aimed at a particular user may becomeproportionately less.

Therefore, in other embodiments, carriers which are subject tocontiguous empty/low power slots are not used for the forward link.Instead, they are used for the return link. Consequently, in someembodiments, at least part of the ATC is configured in reverse frequencymode compared to the SBC in order to allow maximum data rates over theforward link throughout the entire network. On the reverse frequencyreturn link, a radiotelephone may be limited to a maximum of 5 slots perframe, which can be adequate for the return link. Whether the fiveavailable time slots per frame, on a reverse frequency return linkcarrier, are assigned to one radiotelephone or to five differentradiotelephones, they can be assigned contiguously in these embodiments.As was described in connection with FIG. 12, these five contiguous slotscan be assigned to high-power users while the remaining three slots maybe used to serve low-power users.

Other embodiments may be based on operating the ATC entirely in reversefrequency mode compared to the SBC. In these embodiments, an ATCtransmits over the satellite return link frequencies whileradiotelephones respond over the satellite forward link frequencies. Ifsufficient contiguous spectrum exists to support CDMA technologies, andin particular the emerging Wideband-CDMA 3G standard, the ATC forwardlink can be based on Wideband-CDMA to increase or maximize datathroughput capabilities. Interference with GPS may not be an issue sincethe ATCs transmit over the satellite return link in these embodiments.Instead, interference may become a concern for the radiotelephones.Based, however, on embodiments of FIGS. 11-12, the radiotelephones canbe configured to transmit GSM since ATC return link rates are expected,in any event, to be lower than those of the forward link. Accordingly,the ATC return link may employ GPRS-based data modes, possibly evenEDGE. Thus, return link carriers that fall within a predeterminedfrequency interval from the GPS band-edge of 1559 MHz, can be underloaded, per embodiments of FIG. 11 or 12, to satisfy GPS interferenceconcerns.

Finally, other embodiments may use a partial or total reverse frequencymode and may use CDMA on both forward and return links. In theseembodiments, the ATC forward link to the radiotelephones utilizes thefrequencies of the satellite return link (1626.5 MHz to 1660.5 MHz)whereas the ATC return link from the radiotelephones uses thefrequencies of the satellite forward link (1525 MHz to 1559 MHz). TheATC forward link can be based on an existing or developing CDMAtechnology (e.g., IS-95, Wideband-CDMA, etc.). The ATC network returnlink can also be based on an existing or developing CDMA technologyprovided that the radiotelephone's output is gated to ceasetransmissions for approximately 3 msec once every T msec. In someembodiments, T will be greater than or equal to 6 msec.

This gating may not be needed for ATC return link carriers atapproximately 1550 MHz or below. This gating can reduce or minimizeout-of-band interference (desensitization) effects for GPS receivers inthe vicinity of an ATC. To increase the benefit to GPS, the gatingbetween all radiotelephones over an entire ATC service area can besubstantially synchronized. Additional benefit to GPS may be derivedfrom system-wide synchronization of gating. The ATCs can instruct allactive radiotelephones regarding the gating epoch. All ATCs can bemutually synchronized via GPS.

Multi-Band/Multi-Mode Satellite Radiotelephone Communications Systemsand Methods

Some embodiments of the present invention that were described above mayuse the same satellite radiotelephone link band and satellite feederlink band for space-based communications with radiotelephones in allsatellite cells of the satellite footprint or service area. Moreover,some embodiments of the present invention that were described above mayuse the same satellite radio frequency band and substantially the sameair interface for terrestrial communications with radiotelephones usingan ancillary terrestrial network. Other embodiments of the presentinvention that will now be described may use more than one band and/ormore than one air interface in various satellite cells in the satellitefootprint or service area. In still other embodiments, althoughdifferent bands and/or different air interfaces may be used in differentsatellite cells or within a satellite cell, the satellite radiotelephonefrequency band and the air interface that is used for terrestrialcommunications between an ancillary terrestrial network andradiotelephones within a given satellite cell, is substantially the sameas is used for space-based communications with the radiotelephoneswithin the given satellite cell or in different satellite cells.

As used herein, “substantially the same” band means that the bandssubstantially overlap, but that there may be some areas of non-overlap,for example at the band ends. Moreover, “substantially the same” airinterface means that the air interfaces are similar but need not beidentical. Some changes may be made to the air interface to account fordifferent characteristics for the terrestrial and satelliteenvironments. For example, a different vocoder rate may be used (forexample, 13 kbps for GSM and 4 kbps for satellite), a different forwarderror correction coding and/or a different interleaving depth may beused.

Multi-band/multi-mode satellite radiotelephone communications systemsand methods according to some embodiments of the present invention maybe used when a satellite footprint or service area spans a geographicarea in which two or more terrestrial radiotelephone systems (wirelessnetwork operators) are present, to add spaced-based communicationscapability to two or more terrestrial networks. Within a geographic areathat is covered by a given terrestrial radiotelephone system,embodiments of the invention can provide additional capacity and/orextended services using the space-based component and/or the ancillaryterrestrial network, using substantially the same band and/or airinterface as the terrestrial radiotelephone system. Thus, differentgeographic regions corresponding to different terrestrial radiotelephonecommunications systems and methods according to embodiments of theinvention may use different bands and/or air interfaces forcompatibility with the terrestrial radiotelephone systems that arelocated within the different geographic areas. There also may be otherscenarios wherein it may be desired for a single satelliteradiotelephone communications system/method to employ different bandsand/or air interfaces over the same and/or different geographic regionsthereof.

FIG. 16 is a schematic diagram of satellite radiotelephone systems andmethods according to some embodiments of the invention. As shown in FIG.16, these embodiments of satellite radiotelephone systems and methodsinclude a space-based component 1610 that is configured to communicatewith radiotelephones 1620 a-1620 c in a satellite footprint 1630 that isdivided into a plurality of satellite cells 1640 a-1640 c. It will beunderstood by those having skill in the art that, although threesatellite cells 1640 a-1640 c and three radiotelephones 1620 a-1620 care illustrated in FIG. 16, satellite radiotelephone systems and methodsaccording to embodiments of the present invention may employ more thanthree satellite cells 1640 a-1640 c and may employ more than threeradiotelephones 1620 a-1620 c.

Still referring to FIG. 16, the space-based component 1610 is configuredto communicate with a first radiotelephone 1620 a in a first satellitecell 1640 a over a first frequency band and/or a first air interface,and to communicate with a second radiotelephone 1620 b in a secondsatellite cell 1640 b over a second frequency band and/or a second airinterface. In other embodiments, the first radiotelephone 1620 a and thesecond radiotelephone 1620 b may be in the same satellite cell.

Still referring to FIG. 16, in some embodiments of the presentinvention, an ancillary terrestrial network 1650 is configured tocommunicate terrestrially with the first radiotelephone 1620 a oversubstantially the first frequency band and/or substantially the firstair interface, and to communicate terrestrially with the secondradiotelephone 1620 b over substantially the second frequency bandand/or substantially the second air interface. These substantially thesame first frequency band and/or first interface in the first satellitecell 1640 a and in the portion of the ancillary terrestrial network 1650therein, is illustrated by the vertical dashed lines that cover thefirst satellite cell 1640 a and the portion of the ancillary terrestrialnetwork 1650 therein. The substantially the same second frequency bandand/or second air interface in satellite cell 1640 b and in the portionof the ancillary terrestrial network 1650 therein, is illustrated by thehorizontal dashed lines that cover the second satellite cell 1640 b andthe portion of the ancillary terrestrial network 1650 therein.

It will be understood that in FIG. 16, the ancillary terrestrial network1650 is illustrated as including a small number of ancillary terrestrialnetwork cells for simplicity. However, more ancillary terrestrialnetwork cells may be present in some embodiments of the presentinvention. Moreover, it also will be understood that, in someembodiments, a first portion of the ancillary terrestrial network 1650within satellite cell 1640 a may be operated by a first wireless networkoperator and a second portion of the ancillary terrestrial network 1650within the first satellite cell 1640 a or within the second satellitecell 1640 b may be operated by a second wireless network operator.Accordingly, some embodiments of the invention provide systems andmethods for adding space-based communications to first and secondterrestrial networks.

Referring again to FIG. 16, satellite radiotelephone systems and methodsaccording to some embodiments of the present invention also include agateway 1660 that is configured to communicate with the space-basedcomponent 1610 over a feeder link 1670. The feeder link 1670 isconfigured to transport communications between the space-based component1610 and the first and second radiotelephones 1620 a, 1620 b. In someembodiments, the feeder link 1670 comprises the first air interface andthe second air interface. Finally, it also will be understood that athird satellite cell 1640 c, a third radiotelephone 1620 c, and asubstantially the same third frequency band and/or air interface isillustrated by oblique dashed lines in satellite cell 1640 c. In otherembodiments, the third radiotelephone 1620 c is in the same cell as thefirst radiotelephone 1620 a and/or the second radiotelephone 1620 b.

FIG. 17 is a schematic diagram of satellite radiotelephone systems andmethods according to other embodiments of the present invention. Asshown in FIG. 17, a space-based component 1710 is configured tocommunicate with a first radiotelephone 1720 a over a first frequencyband and/or first air interface 1780 a, also designated in FIG. 17 byF1/I1. As also shown in FIG. 17, the space-based component 1710 is alsoconfigured to communicate with a second radiotelephone 1720 b over asecond frequency band and/or a second air interface 1780 b, alsodesignated in FIG. 17 by F2/I2. An ancillary terrestrial network 1750 isconfigured to communicate terrestrially with the first radiotelephone1720 a over substantially the first frequency band and/or substantiallythe first air interface 1790 a, also designated in FIG. 17 as F1′/I1′,and to communicate terrestrially with the second radiotelephone 1720 bover substantially the second frequency band and/or substantially thesecond air interface 1790 b, also designated in FIG. 17 as F2′/I2′. Theancillary terrestrial network 1750 may be included within a singlesatellite cell or may spread across multiple satellite cells.

As also shown in FIG. 17, the ancillary terrestrial network can comprisea first ancillary terrestrial component 1752 a that is configured tocommunicate terrestrially with the first radiotelephone 1720 a oversubstantially the first frequency band and/or substantially the firstair interface 1790 a. A second ancillary terrestrial component 1752 b isconfigured to communicate terrestrially with the second radiotelephone1720 b over substantially the second frequency band and/or substantiallythe second air interface 1790 b. As was the case in FIG. 16, a largenumber of radiotelephones 1720 and/or ancillary terrestrial components1752 may be provided in some embodiments. The first and second ancillaryterrestrial components 1752 a, 1752 b, respectively, may be parts of twoseparate wireless networks in the same and/or different satellite cells,in some embodiments. Thus, some embodiments of FIG. 17 provide systemsand methods for adding space-based communications to first and secondterrestrial networks. A gateway 1760 and a feeder link 1770 may beprovided, as was described in connection with FIG. 16.

Some embodiments of the present invention provide satelliteradiotelephone systems and/or methods that include radiotelephone linksthat are operative over a plurality of bands. In some embodiments, theband-sensitive (i.e., frequency-sensitive) components of the space-basedcomponent 1610, 1710, such as the antenna feed network, the poweramplifiers, the low noise amplifiers, etc., may be designed to bebroadband, so that the operational range of the space-based componentcan extend over a plurality of service link bands, such as L-band,S-band, etc. In other embodiments, separate components for each band maybe provided. In still other embodiments, some common broadbandcomponents and some separate narrowband components may be provided.

Moreover, other embodiments of the present invention may provide amulti-mode payload capacity, by providing a plurality of air interfacesthat may be used to provide radiotelephone communications with thespace-based component 1610, 1710 and a plurality of radiotelephones1620, 1720 in a satellite footprint over the same and/or a plurality ofsatellite cells. The space-based component 1610, 1710 may be configuredto support a plurality of air interface standards, for example by havinga programmable channel increment that can be responsive to groundcommands. Different channel increments, for example, may be applied bythe space-based components 1620, 1720 to different bands of the receivedfeeder link signal 1670, 1770 from a gateway 1660, 1760. These differentbands of the feeder link spectrum may remain constant or may change withtime, depending on the traffic carried by each air interface standardthat may be supported by the satellite radiotelephone system.

Thus, in some embodiments, the feeder link 1670, 1770 may be segmentedinto bands, such as bands B₁, B₂ and B₃. In one example, band B₁ cantransport GSM carriers between the gateway and the space-basedcomponent, band B₂ can transport narrowband CDMA carriers and band B₃may transport wideband CDMA carriers. It will be understood by thosehaving skill in the art that corresponding return feeder link bands maybe provided for carriers from the space-based component 1610, 1710 tothe gateway 1660, 1760. In other embodiments of the present invention,an ancillary terrestrial network 1650, 1750 also may be provided tocommunicate terrestrially with radiotelephones 1620, 1720 in thesatellite footprint. Thus, in some embodiments, the ancillaryterrestrial network 1650, 1750 may provide a larger portion of theradiotelephone communications in urban areas, whereas the space-basedcomponent 1610, 1710 may provide a larger portion of the radiotelephonecommunications in rural areas.

FIG. 13 is a block diagram of satellite radiotelephone systems and/ormethods that can use multiple bands and/or multiple modes according tosome embodiments of the present invention. It will be understood bythose having skill in the art that FIG. 13 relates to GSM, and systemelements that provide a GSM air interface are shown. However, othersatellite radiotelephone systems and/or methods also may be providedaccording to embodiments of the present invention.

In particular, as shown in FIG. 13, these embodiments of satelliteradiotelephone communication systems and methods include a space-basedcomponent 1310, for example a geostationary satellite, and at least oneGateway Station System (GSS) 1360, Network Operation Center (NOC) 1362,Mobile Switching Center (MSC) 1364, Base Station Controller (BSC) 1366and Base Transceiver Station (BTS) 1368. The satellite radiotelephonesystem may be connected to the Public Switched Telephone Network (PSTN)1772 and/or to one or more Public Data Networks (PDN) 1774. In addition,to offer a General Packet Radio Service (GPRS), some MSCs 1364 may beaugmented by appropriate packet switching facilities, generally referredto as Support GPRS Service Node (SGSN) and GPRS Gateway Support Node(GGSN). The GSS also may be connected to a Tracking Telemetry & Command(TT&C) system 1776. A plurality of radiotelephones 1320 also may beprovided.

FIG. 14 illustrates frequency reuse between a space-based component andan ancillary terrestrial network according to some embodiments of thepresent invention. As shown in FIG. 14, relatively small ancillaryterrestrial network cells 1450 are nested inside the relatively largesatellite cells 1440. This may occur because, even with large reflectorsthat may be used in the space-based component 1410, the satellite cells1440 may still be on the order of several hundred kilometers indiameter, whereas the ancillary terrestrial network cells 1450 may betwo, three or more orders of magnitude smaller than the satellite cells.In FIG. 14, terrestrial reuse of the same carrier frequency is indicatedby the same symbol (●, □ or *).

Embodiments of the present invention as shown in FIGS. 13 and 14 canallow a single satellite radiotelephone system to support a plurality ofancillary terrestrial components 1452 in an ancillary terrestrialnetwork 1450, with at least some of the ancillary terrestrial components1452 providing terrestrial connectivity via a different air interface.This may allow the relatively large satellite footprint 1430 to be usedin a terrestrial market which is segmented. Thus, in some embodiments,the satellite radiotelephone system may be configured to support aGSM-based ancillary terrestrial component, a narrowband CDMA-basedancillary terrestrial component, and a wideband CDMA-based ancillaryterrestrial component, at the same time and over the same or differentsatellite cells. In other embodiments, a subset of the ancillaryterrestrial components may be operating at L-band, for example, whileanother subset of ancillary terrestrial components may be operating atS-band.

As was already described, in some embodiments, satellite radiotelephonecommunications systems and methods can provide substantially the sameband/same air interface service for both space-based communications withthe space-based component and terrestrial communications with at leastone of its ancillary terrestrial components. This can allow simplifiedradiotelephones.

In particular, FIG. 15 is a block diagram of radiotelephones 1520 thatmay be used to communicate with a space-based component and an ancillaryterrestrial component in satellite radiotelephone systems or methodsaccording to some embodiments of the present invention. In someembodiments, these radiotelephones 1520 can be used with satelliteradiotelephone systems according to some embodiments of the presentinvention that include an ancillary terrestrial component and aspace-based component that use substantially the same band andsubstantially the same air interface. The ability to reuse the samespectrum for space-based and terrestrial communications can facilitatelow cost, small and/or lightweight radiotelephones, according to someembodiments of the present invention.

Moreover, some embodiments of the present invention can place more ofthe burden of link performance with the space-based component ratherthan the radiotelephone, compared to prior satellite radiotelephonesystems, such as Iridium or Globalstar. Accordingly, large antennas maynot need to be used in the radiotelephone. Rather, antennas that aresimilar to conventional cellular radiotelephone antennas may be used.

Accordingly, referring to FIG. 15, a single Radio Frequency (RF) chainincluding low pass filters 1522, up and down converters 1524 a, 1524 b,Local Oscillators (LO) 1526, Low Noise Amplifier (LNA) 1528, PowerAmplifier (PA) 1532, bandpass filters 1534 and antenna 1536, may beused. A single baseband processor 1542 may be used, including ananalog-to-digital converter (A/D) 1544, a digital-to-analog converter(D/A) 1546 and a Man-Machine Interface (MMI) 1548. An optional Bluetoothinterface 1552 may be provided. An Application-Specific IntegratedCircuit (ASIC) 1554 may include thereon Random Access Memory (RAM) 1556,Read-Only Memory (ROM) 1558, a microprocessor (μP) 1562, logic forancillary terrestrial communications (ATC Logic) 1564 and logic forspace-based communications (Space Segment Logic or SS Logic) 1566. TheSS Logic 1566 can be used to accommodate satellite-unique requirementsover and above those of cellular or PCS, such as a satellite-uniquevocoder, a satellite forward error correction coding scheme, asatellite-unique interlever, etc. However, this added gate count may notincrease the cost of the ASIC 1554.

According to other embodiments of the invention, the space-basedcomponent may be dimensioned appropriately, so that there is no need forradiotelephones to use large antennas 1536 or to have to radiate anymore power when in satellite mode than when in terrestrial mode. Anappropriate level of link robustness may be attained via the spot-beamgain that can be provided by a larger satellite antenna and/or othertechniques. This can more than compensate for the several dB reductionin satellite link robustness that may occur when eliminating a largesatellite antenna from the radiotelephone and/or using a single antennafor terrestrial and satellite communications. Accordingly, single modeand single band radiotelephones may be provided that can communicatewith the space-based component and the ancillary terrestrial networkover a single band and single air interface.

Aggregate Radiated Power Control for Multi-Band/Multi-Mode SatelliteRadiotelephone Communications Systems and Methods

Multi-band/multi-mode satellite radiotelephone communications systemsand methods according to other embodiments of the present invention nowwill be described.

In particular, referring to FIG. 18, a satellite radiotelephone systemincludes a space-based component 1610 that is configured to communicatewith a plurality of radiotelephones over a plurality of frequency bandsand/or a plurality of air interfaces. The links that use the pluralityof frequency bands and/or air interfaces are denoted in FIG. 18 as 1880a-1880 f, although it will be understood that fewer or more frequencybands/air interfaces may be used. An ancillary terrestrial network (ATN)1850 is configured to communicate terrestrially with the plurality ofradiotelephones over substantially the plurality of frequency bandsand/or substantially the plurality of air interfaces. It will beunderstood that, in FIG. 18, five ancillary terrestrial components (ATC)1852 a-1852 f are shown, although fewer or more ancillary terrestrialcomponents may be employed in the ancillary terrestrial network 1850. Asatellite gateway 1660 and a PDN/PSTN 1810 are also provided as wasalready described.

Still referring to FIG. 18, an aggregate radiated power controller 1820is provided that is configured to limit an aggregate radiated power bythe plurality of radiotelephones to a maximum aggregate radiated power.In some embodiments, the aggregate radiated power controller isconfigured to control a plurality of co-frequency radiotelephones, so asto limit the aggregate radiated power by the plurality of co-frequencyradiotelephones to a maximum aggregate radiated power. As used herein,“co-frequency” means that the radiotelephones use the same carrierfrequency even if they use different TDMA time slots (different TDMAchannels) or use different CDMA spreading codes (different CDMAchannels). Accordingly, compliance with radiation requirements for theancillary terrestrial network 1850 may be maintained even though theancillary terrestrial network 1850 employs a plurality of frequencybands and/or air interfaces. It will be understood that the aggregateradiated power controller 1820 may be provided as a stand alonecomponent, as part of the gateway 1660, and/or as part of anothercomponent of the satellite radiotelephone system and/or the ATN.

In some embodiments of the present invention, the aggregate radiatedpower controller 1820 is configured to allow control over substantiallyall of the ATN and/or substantially all of the radiotelephones that arecommunicating therewith. However, in other embodiments of the presentinvention, the aggregate radiated power controller 1820 is configured tolimit an aggregated radiated power by a subset of the plurality ofradiotelephones to a maximum aggregate radiated power. For example, insome embodiments, the plurality of frequency bands comprises a firstfrequency band and a second frequency band, and the subset of theplurality of radiotelephones comprises radiotelephones that communicateterrestrially with the ancillary terrestrial network over substantiallythe first frequency band. In some embodiments, the first frequency bandcomprises L-band frequencies and, in some embodiments, the secondfrequency band comprises S-band frequencies. In other embodiments, thefirst frequency band comprises L-band frequencies that are usedsubstantially inter-radio-horizon by another system and the secondfrequency band comprises L-band frequencies that are not usedsubstantially inter-radio-horizon by another system. In theseembodiments, the second frequency band may further comprise S-bandfrequencies.

Thus, in some embodiments, only a first subset of the ATN, and/or theradiotelephones communicating therewith, may be subject to aggregateradiated power control, whereas a second subset of the ATN, and/or theradiotelephones that are communicating therewith, need not be subject toaggregate radiated power control. For example, L-band frequencies thatare radiated terrestrially may potentially cause interference withanother system, and may be subject to aggregate radiated power control.In contrast, S-band frequencies and L-band frequencies that are not usedsubstantially inter-radio-horizon by another system may not potentiallycause interference with another system, and therefore may not be subjectto aggregate radiated power control, according to embodiments of thepresent invention.

More specifically, a Mobile Satellite System (MSS) including an ATN 1850may provide voice and/or data services to end users over its footprintusing more than one air interface protocol. It may be desirable for thesystem to be capable of providing services to end users via several airinterface protocols given the current fragmentation and potential futureuncertainty of the U.S. radiotelephone communications market. Currently,the U.S. market may be serviced by iDEN, GSM and cdma2000, but otheremerging standards, such as W-CDMA and/or OFDM/OFDMA, may be used in thefuture. A system architecture that lends itself to the plurality ofcurrent standards (air interface protocols) and can also accommodatefuture (currently anticipated or not) technologies can offer increasedflexibility.

FIG. 18 illustrates a potential deployment scenario for the ATN. Asshown, different and/or overlapping geographical areas may be served byATCs 1852 a-1852 f that are using different air interface protocols. Thesatellite 1610 is capable of transporting the plurality of protocolsto/from the satellite gateway 1660 where different sets of transceiverunits may be associated with the processing of the different airinterface waveforms. The radiotelephone may contain an integratedtransceiver capable of communicating via the satellite 1610 or via atleast one ATC 1852, and potentially over other PCS/cellular bands,depending, for example, on business relationships that may beestablished with other wireless operators. The satellite/ATN part of theradiotelephone transceiver may utilize substantially the same airinterface protocol to communicate via the satellite 1610 or via at leastone ATC 1852. This approach can reduce or minimize the size, weightand/or manufacturing cost of the transceiver by increasing the level ofintegration and reuse of hardware and software for both satellite andATN modes.

In some embodiments of the invention, the ATN may be based on a CDMA airinterface protocol without producing any greater interference potentialthan the Federal Communications Commission rules allow for a GSM-basedATN. See, Report and Order and Notice of Proposed Rulemaking, FCC 03-15,Flexibility for Delivery of Communications by Mobile Satellite ServiceProviders in the 2 GHz Band, the L-Band, and the 1.6/2.4 Bands, IBDocket No. 01-185, Adopted: Jan. 29, 2003, Released: Feb. 10, 2003,hereinafter referred to as “FCC 03-15”. Thus, the technology used by theATN or any of its ATCs can be irrelevant as long as the aggregateco-frequency emissions level is controlled so as not to exceed the limitset forth by the Commission for the specific GSM system considered inFCC 03-15. As such, an ATN 1850 can be developed to function with aplurality of air interface protocols simultaneously, as long as itadheres to the aggregate radiated power spectral density limit set forthby the Commission (i.e., −53+10 log(1,725) dBW/Hz).

In FCC 03-15, the Commission allowed 1,725-fold terrestrial reuse, bythe US ATN, of a GSM carrier that is also used by the MSS for satellitecommunications. A single fully-loaded GSM carrier on an ATC return link,which is being radiated from several radiotelephones (up to eight) to abase station, may launch a maximum −53 dBW/Hz of power spectral densityinto space. The maximum aggregate power spectral density that may belaunched into space from 1,725 co-channel fully loaded return-link GSMcarriers is, therefore, −53+10 log(1725)≈−20.64 dBW/Hz. This is based ona GSM radiotelephone peak EIRP of 0 dBW, consistent with the analysis ofFCC 03-15. It is this maximum aggregate power spectral density, producedon the return link by the maximum allowed US-wide frequency reuse of theATN, that the Commission has concluded may potentially raise the noisefloor of Inmarsat's satellite receivers by as much as 0.7%.

The maximum EIRP of a CDMA return link code (user) may be −10 dBW andmay be transmitted over a carrier occupying a bandwidth of 1.25 MHz inaccordance, for example, with the cdma2000 air interface standard. Thus,−10−10 log(1,250,000)≈−70.97 dBW/Hz of power spectral density may belaunched into space by a single CDMA code (user) operating on an ATCreturn link. The allowed −20.64 dBW/Hz maximum aggregate power spectraldensity limit, as derived above, may therefore accommodate approximately10^([(70.97−20.64)/10])≈107,894 co-channel return link CDMA codes. Thisresult may be used to establish an equivalence relation, for the ATNreturn link, between a pure GSM ATN and a pure CDMA ATN.

Thus, from an aggregate return link interference power spectral densitystandpoint, 1,725-fold US-wide frequency reuse of a GSM carrier by theATN may be considered equivalent to approximately 107,894 codes (users)transmitting US-wide on a given 1.25 MHz CDMA carrier. The number ofusers is generally less than or equal to the number of codes, because auser may be allocated more than one code to improve the reliabilityand/or data rate of transmission. The stated equivalence is based onGSM's peak return link EIRP assumed to be 0 dBW while that of a CDMAcode is assumed to be −10 dBW.

A mathematical equivalence may be established between a single active(transmitting) GSM time slot (user) transmitting at a peak EIRP of 0dBW, and a number of CDMA codes (users) being active and eachtransmitting at a peak EIRP of −10 dBW. This relationship can allowdeploying an ATN that contains both GSM and CDMA technologies, andpotentially fluctuating capacity between the two, and is, from the pointof view of aggregate return link interference power spectral densitypotential, equivalent to the pure GSM system that the Commissionaddressed in FCC 03-15.

In particular, according to FCC 03-15, there are 1,725×8=13,800 GSM timeslots (users) that can be active on the ATN (US-wide) on a given GSMcarrier while maintaining the potential for noise increase to Inmarsat'ssatellite receivers at 0.7%. It was shown above that, from an aggregateup-link power spectral density interference potential standpoint, thisis equivalent to approximately 107,894 codes (users) transmitting on agiven 1.25 MHz CDMA carrier (US-wide). Thus, one active co-frequency GSMslot (user) equates to approximately 107,894/13,800≈7.8184 activeco-frequency CDMA codes (users). Thus, an equation that may be used togovern co-frequency ATN operations over the United States may be:N _(GSM)+13,800N _(CDMA)/107,894=13,800.  (1)

In Equation (1), N_(GSM) denotes the number of active co-frequency GSMtime slots (users) while N_(CDMA) denotes the number of activeco-frequency CDMA codes (users). In some embodiments, the N_(GSM) GSMtime slots are at least partially co-frequency with the N_(CDMA) CDMAcodes. Since there are 6 distinct GSM carriers that can be co-frequencywith a single CDMA carrier of 1.25 MHz bandwidth, the co-frequency CDMAcarrier loading will deplete, by the same amount of13,800N_(CDMA)/107,894, the US-wide capacity of all 6 corresponding(co-frequency with the CDMA carrier) GSM carriers. Based on the above,it is seen that a US-wide ATN network that is configured to supportsimultaneously both GSM and cdma2000 traffic can be compliant with theCommission's uplink interference constraint (no more than 0.7% ΔT/Timpact to, for example, Inmarsat) if and only if Equation (1) issubstantially satisfied. The MSS/ATN operator may comply by apportioningthe total co-frequency traffic in such an ATN substantially inaccordance with Equation (1).

As discussed earlier, a fully-loaded GSM return link carrier (all eighttime slots occupied) may generate −53 dBW/Hz of maximum EIRP densitypotential. This result is based on GSM radiotelephones/radioterminalshaving an antenna gain of, for example, 0 dBi and radiating a maximum 0dBW EIRP over a carrier bandwidth of 200 kHz (in accordance with theFCC's assumptions in FCC 03-15.

A cdma2000 ATN radioterminal having, for example, a 0 dBi antenna gainmay be limited (by design) to a maximum of, for example, −9 dBW EIRPwhile communicating using a single code. Given the 1.25 MHz carrierbandwidth of cdma2000 (1xRTT) the maximum EIRP density that may begenerated by a single cdma2000 return-link code may be −9−10log(1.25×10⁶)≈−70 dBW/Hz. It therefore follows that 10^([(70−53)/10])≈50co-frequency cdma2000 codes may generate the same uplink interferencepower spectral density potential as one fully-loaded GSM carrier.

For W-CDMA, an ATN radioterminal having, for example, a 0 dBi antennagain may be limited (by design) to a maximum of, for example, −9 dBWEIRP while communicating using a single code. Given the 5 MHz carrierbandwidth of W-CDMA, such a radioterminal may generate an EIRP densitypotential of −9−10 log(5×10⁶)≈−76 dBW/Hz. Thus, 10^([(76−53)/10])≈200co-frequency W-CDMA codes may generate the same uplink interferencepower spectral density potential as one fully-loaded GSM carrier.

For an ATN that may be based on all three technologies (GSM, cdma2000,and W-CDMA) the following constraint equation may be used to specify theallowed distribution of on-the-air co-frequency traffic associated withthe three standards:N/8+M/50+L/200=R  (2)where N denotes the number of GSM time slots (channels) supportedATN-wide co-frequency by a given GSM carrier as that carrier is used andreused, M represents the number of cdma2000 co-frequency codes(channels) supported by a single cdma2000 carrier as that carrier isused and reused throughout the ATN, L identifies the number of W-CDMAco-frequency codes (channels) on a single W-CDMA carrier as that carrieris used and reused by the ATN, and R denotes the pure GSM-based ATNfrequency reuse authorized by the FCC. In some embodiments, the N GSMtime slots, the M cdma2000 codes and the L W-CDMA codes are at leastpartially co-frequency. Note that the above equation can provide aconstraint that may be imposed on co-frequency operating carriers (allthree carrier types, GSM, cdma2000, and W-CDMA, whose ATN-wide trafficis apportioned in accordance with the above equation may be operatingco-frequency). Furthermore, for a pure GSM-based ATN deployment, theabove equation reduces to N=8R (M=L=0) which confirms that the totalnumber of time slots (channels) that can be supported by a single GSMcarrier ATN-wide equals eight times the authorized frequency reuse.

Since there are 6 GSM carriers that may fit within the bandwidthoccupied by a single cdma2000 carrier, the nationwide loading (M) of acdma2000 carrier may deplete, by the same amount of M/50, the nationwidecapacity of all 6 corresponding (co-frequency with the cdma2000 carrier)GSM carriers. Similarly, since there are 25 GSM carriers that may existwithin the bandwidth occupied by a single W-CDMA carrier, the nationwideloading (L) of a W-CDMA carrier may deplete, by the same amount ofL/200, the nationwide capacity of all 25 corresponding (co-frequencywith the W-CDMA carrier) GSM carriers. For similar reasons, since thereare 4 cdma2000 carriers that may be accommodated (co-frequency) over theband of frequencies occupied by a W-CDMA carrier, the nationwide loadingof a W-CDMA carrier may deplete, by the same amount of L/4, thenationwide capacity of all 4 corresponding (co-frequency with the W-CDMAcarrier) cdma2000 carriers.

Equations (1) and (2) may be generalized as follows:

$\begin{matrix}{{{\sum\limits_{i = 1}^{x}\frac{N_{i}}{F_{i}}} = {MARP}},} & (3)\end{matrix}$

-   -   where N_(i) is the number of co-frequency active users using a        given frequency band and/or air interface i;    -   F_(i) is a corresponding equivalence factor (which may be less        than, greater than or equal to 1) for the given frequency        band/air interface i; and    -   MARP is a measure of the maximum aggregate radiated power        spectral density that is permitted.

It will be understood that in FCC 03-15, the aggregate radiated PowerSpectral Density (PSD) that may be launched U.S.-wide by radioterminalscommunicating with an ATN may not exceed −53+10 log(1725)≈−20.6 dBW/Hz.In arriving at this conclusion the FCC assumed that the ATN will bebased on GSM technology and that the GSM radioterminals will be capableof launching in the direction of a co-frequency satellite system (e.g.,Inmarsat) a maximum (uplink) EIRP of 0 dBW per carrier. The FCC'sconclusion is also based on the assumption that only 50% of the ATN isinside the U.S.

The aggregate radiated U.S.-wide PSD may be higher if more than 50% ofthe ATN is allowed to be inside the U.S. For example, based on 80%deployment of the total ATN inside the US, the aggregate allowed US-widePSD potential may grow to −53+10 log(2760)≈−18.6 dBW/Hz. In FCC 03-15,the Commission concluded that the aggregate average signal attenuationthat is relevant to uplink interference is 242.7 dB. This number takesinto account attenuation/suppression of the interfering signal(s) due to(a) free-space propagation (188.7 dB), (b) co-frequency system satelliteantenna discrimination in the direction of the ATN (25 dB), (c) outdoorblockage (3.1 dB), (d) closed-loop power control implemented by the ATN(20 dB), (e) use of a lower-rate vocoder (3.5 dB), (f) voice activity (1dB), and (g) polarization discrimination provided by the co-frequencysatellite system (1.4 dB). (See FCC 03-15, Appendix C2, Table 2.1.1.C,page 206). The interference signal suppression due to power control (20dB) comprises 2 dB due to “range taper” and 18 dB due to structuralattenuation. Based on the Commission's conclusions/assumptions, asspecified in FCC 03-15, and assuming deployment of up to 80% of the ATNinside the US, the aggregate average PSD potential at the input of aco-frequency satellite antenna may be limited to −18.6−242.7=−261.3dBW/Hz.

As was described above, aggregated radiated power controlling systemsand methods according to some embodiments of the present invention, maybe configured to limit an aggregate radiated power by a plurality ofradiotelephones to a maximum aggregate radiated power. In embodimentsthat were described above, it was assumed that the ATN has the sameamount of structural attenuation margin and/or return link margin acrossall ancillary terrestrial components thereof, that use a given frequencyband and/or carrier frequency and/or air interface. The calculationsthat were described above were made under this assumption. However, thismay not always be the case. Rather, according to other embodiments ofthe present invention, various ATCs in the ATN may provide differentstructural attenuation and/or return link margins. In fact, according toother embodiments of the present invention, link margins may beincreased in various ATCs, to allow larger numbers of radioterminals tocommunicate terrestrially without exceeding a maximum aggregate radiatedpower. Two illustrative examples will be provided. In a first example, aplurality of cdma2000 radioterminals communicate with ATN infrastructurethat provides 18 dB of structural attenuation margin. In a secondexample, not all of the ATN infrastructure provides 18 dB of structuralattenuation margin.

Thus, in the first example, all cdma2000 ATC radioterminals communicatewith infrastructure that provides 18 dB of structural attenuationmargin. Relative to a satellite, a cdma2000 ATN radioterminal mayradiate, for example, a maximum (spatially averaged) EIRP of −13 dBW percommunications channel (i.e., per code; the EIRP consumed by the pilotchannel is neglected for the sake of simplicity). Hence, theradioterminal's PSD potential, per communications channel, may be −74dBW/Hz (at the radioterminal's antenna output) and −74−242.7=−316.7dBW/Hz at the satellite's antenna input. The number of suchradioterminals (communications channels) that operate co-frequency inorder to generate the allowed PSD potential of −261.3 dBW/Hz, at theinput of a satellite antenna, is 10^([(316.7−261.3)/10])=346,736. Insome embodiments, up to seven (7) cdma2000 carriers may be deployed inthe ATN. Thus, the total on-the-air capacity of a U.S.-based ATN may be346,736×7=2,427,152 simultaneous communications channels.

In the second example, not all radioterminals are communicating withinfrastructure that provides 18 dB of structural attenuation margin. Forexample, let X, Y, and Z denote US-wide potential percentages (%) of ATNcdma2000 radioterminals that may be communicating co-frequency with ATNinfrastructure that is providing A, B, and C dB, respectively, ofstructural attenuation margin. Thus:X+Y+Z=100.  (4)Letting L, M, and N denote the number of potential radioterminals thatmay be communicating with class A, B, and C infrastructure,respectively, we may write:X=100L/(L+M+N), Y=100M/(L+M+N), Z=100N/(L+M+N).  (5)Subject to the three classes/categories of ATN infrastructure (asdefined above) that may be serving the ATN radioterminals, the aggregatepower spectral density potential (in Watts/Hz) at a satellite antennainput may be:psd=[Lξ+Mζ+Nç]σ ² Watts/Hz.  (6)In Equation (6), the quantity 10 log(σ²) may, for example, be specifiedas −74 dBW/Hz, and ξ, ζ, and ç, may denote average aggregate(power-domain) attenuation factors associated with the three classes ofradioterminals that may be served by the three classes ofinfrastructure, respectively. Thus, we may write:10 log(ξ)=−(188.7+25+3.1+(A+2)+3.5+1+1.4)=−(224.7+A)dB  (7)10 log(ζ)=−(188.7+25+3.1+(B+2)+3.5+1+1.4)=−(224.7+B)dB; and  (8)10 log(ç)=−(188.7+25+3.1+(C+2)+3.5+1+1.4)=−(224.7+C)dB.  (9)Using Equation (5):N=L[(100−X)(100−Y)−XY]/100X, and M=100YL/[(100−Y)(100−Z)−YZ].  (10)Substituting Equations (7) through (10) into Equation (6) and taking thelogarithm, the average PSD potential at a victim satellite may beexpressed as:PSD≡10 log(psd)=10 log(σ²)+10 log(L)+10log(10^(−(22.47+0.1A))+10^(−(22.47+0.1B))×100Y/[(100−Y)(100−Z)−YZ]+10^(−(224.7+0.1C))×[(100−X)(100−Y)−XY]/100X),  (11)or−261.3=−74+10 log(L)+10log(10^(−(22.47+0.1A))+10^(−(22.47+0.1B))×100Y/[(100−Y)(100−Z)−YZ]+10^(−(22.47+0.1C))×[(100−X)(100−Y)−XY]/100X).  (12)Solving for L:L=10^(−18.73−log( ))  (13)In Equation 13, the second term of the exponent “log( )” is defined byEquation (12). That is:log()≡log(10^(−(22.47+0.1A))+10^(−(22.47+0.1B))×100Y/[(100−Y)(100−Z)−YZ]+10^(−(22.47+0.1C))×[(100−X)(100−Y)−XY]/100X)  (14)Once L is found from Equation (13), N and M may be evaluated usingEquations (5) as follows:N=L[(100−X)(100−Y)−XY]/100X, and M=Y(L+N)/(100−Y)  (15)The following Table provides illustrative numerical results:

TABLE X(%)/A(dB) Y(%)/B(dB) Z(%)/C(dB) L M N L + M + N (L + M + N) × 7100/18   0/18  0/18 346,736 0 0 346,736 2,427,152 60/22 30/12 10/668,859 34,439 11,499 114,797 803,579 30/18 60/12 10/6 24,349 48,6858,108 81,142 567,994

Accordingly, the second example that was described above may provideadditional embodiments of Equation (3), wherein N_(i) denotes a numberof co-frequency channels that are operative subject to a common (i^(th))structural attenuation margin for a given frequency band and/or carrierfrequency and/or air interface, F_(i) denotes a correspondingequivalence factor, which may be less than, greater than, or equal to 1,for the common (i^(th)) structural attenuation margin for the givenfrequency band/carrier frequency/air interface, and MARP is a measure ofthe maximum aggregated radiated power, i.e., the maximum aggregateradiated Power Spectral Density (PSD).

In some embodiments of the invention, an ATN may be configured tomaintain a list of infrastructure components (i.e., base stations and/orbase station groupings), and associate with each infrastructurecomponent a measure of Structural Attenuation Margin (SAM). Based on theregistration procedure of radioterminals, and/or other means, the ATNmay also be configured to have knowledge of the infrastructure componentwith which each active (on-the-air) radioterminal is communicating.Thus, the ATN may be configured to associate a SAM with each activeradioterminal and may thus be configured to evaluate the quantityΣ_(i)(psd)_(i), where psd denotes a power spectral density at asatellite and where the summation may be performed over an ensemble ofactive (on-the-air) radioterminals that are operating co-frequency inthe ATN (i.e., are sharing in whole or in part an ATN band and/orsub-band of frequencies). In some embodiments of the invention, thequantity (psd)_(i) may be evaluated for the i^(th) co-frequencyradioterminal as:(psd)_(i)=10^([log(p) ^(i) ^(/BW) ^(i) ^()+log(α) ^(i) ^()]),  (16)where the quantity 10 log(p_(i)) may denote a measure of the maximumEIRP in the direction of a satellite that may be generated by the i^(th)active (on-the-air) radioterminal (e.g., −4 dBW for GSM, −13 dBW forcdma2000 and/or W-CDMA), BW_(i) may denote a measure of the bandwidthoccupied by the carrier being radiated by the i^(th) activeradioterminal (e.g., 200 kHz for GSM, 1.25 MHz for cdma2000, and 5 MHzfor W-CDMA), and 10 log(α_(i)) may denote a measure of aggregate signalattenuation that may exist between the i^(th) radioterminal and asatellite.

The quantity 10 log(α_(i)) may further be expressed as 10log(α_(i))=−(L+SAM_(i))dB, where L is defined as a measure of aggregatesignal attenuation potential comprising, for example, (a) free-spacepropagation (i.e., 188.7 dB), (b) co-frequency satellite antennadiscrimination (i.e., 25 dB), (c) outdoor blockage (i.e., 3.1 dB), (d)ATN power control due to range taper (i.e., 2 dB), (e) effect oflow-rate vocoder (i.e., 3.5 dB), (f) effect of voice activity (i.e., 1dB), and (g) polarization discrimination provided by co-frequencysatellite antenna (i.e., 1.4 dB). (See FCC 03-15 Appendix C2, Table2.1.1.C; page 206). SAM_(i) may denote a measure of structuralattenuation margin provided by the infrastructure component (i.e., abase station and/or a group of base stations) with which the i^(th)active co-frequency radioterminal is communicating. Typical values ofSAM_(i) may be, for example, 22 dB, 18 dB, 12 dB, and 6 dB, fordense-urban, urban, sub-urban, and rural infrastructure components,respectively.

Accordingly, in some embodiments of the present invention, the aggregateradiated power controller is configured to control a plurality ofco-frequency radioterminals, so as to limit the aggregate radiated powerby the plurality of radioterminals to a maximum aggregate radiated poweraccording to:

$\begin{matrix}{{{\sum\limits_{i = 1}^{x}({psd})_{i}} = {MARP}},} & (17)\end{matrix}$where (psd)_(i) is a measure of radiated power spectral density at asatellite and MARP is a measure of allowed maximum aggregate radiatedpower. In some embodiments, psd is determined according to(psd)_(i)=10^([log(p) ^(i) ^(/BW) ^(i) ^()+log(α) ^(i) ⁾]; where 10log(p_(i)) denotes a measure of maximum radiated power by the i^(th)radioterminal in a direction of a satellite, BW_(i) denotes a bandwidthoccupied by a carrier that is radiated by the i^(th) radioterminal and10 log(α_(i)) denotes a measure of signal attenuation (in dB) betweenthe i^(th) radioterminal and the satellite.

The ATN may evaluate the quantity Σ_(i)(psd)_(i), and/or another measurethereof, as needed, and may, in response to the value of Σ_(i)(psd)_(i),and/or the value of the other measure, approaching, being equal to, orhaving exceeded a threshold value, control the ancillary terrestrialnetwork and/or one or more of the radioterminals to limit the aggregateradiated power to a maximum aggregate radiated power.

Many techniques may be used to limit the aggregate radiated power. Forexample, in some embodiments, one or more co-frequency radioterminalsmay be commanded to 1) utilize a lower-rate vocoder, and/or 2) to reducethe rate of information transmission, and/or 3) to use other availableATN or non-ATN resources that may not be co-frequency with the resourcesthat are relevant to the quantity Σ_(i)(psd)_(i) (i.e., a frequency thathas not exceeded the maximum aggregate radiated power) and/or anothermeasure thereof. Thus, in some embodiments, the aggregate radiated powercontroller is configured to control the plurality of radioterminals byreducing a vocoder rate of at least one of the radioterminals, and/orreducing a rate of information transmission of at least one of theradioterminals, and/or controlling at least one of the radioterminals tocommunicate using a frequency that has not exceeded the maximumaggregate radiated power, so as to limit an aggregate radiated power bythe plurality of co-frequency radiotelephones to the maximum aggregateradiated power.

Many different techniques also may be used to determine whichradioterminal and/or which portion of the ancillary terrestrial networkto control to reduce the aggregate radiated power, according to variousembodiments of the present invention. Thus, in some embodiments, atleast one radioterminal is selected and controlled as described above,so as to reduce the aggregate radiated power. In other embodiments, atleast one radioterminal that is subject to a low, and in someembodiments a lowest, structural attenuation margin and which is,therefore, radiating at a relatively high level, may be controlledaccording to any of the embodiments described above.

Moreover, in other embodiments, a radioterminal may be selected based onthe frequency band and/or carrier frequency and/or air interface that itis using, so that if a given frequency band and/or carrier frequencyand/or air interface exceeds a desired maximum aggregate radiated power,one or more radioterminals that is/are using that frequency band and/orcarrier frequency and/or air interface may be controlled. Accordingly,in some embodiments, the aggregate radiated power controller isconfigured to control a plurality of radioterminals, by controlling atleast one radioterminal that is communicating with the ATN over afrequency band and/or carrier frequency and/or air interface that hasexceeded a maximum aggregated radiated power for that frequency bandand/or carrier frequency and/or air interface, so as to limit theaggregate radiated power by the plurality of radioterminals for thefrequency band and/or carrier frequency and/or air interface to amaximum aggregate radiated power for the frequency band and/or carrierfrequency and/or air interface. A priori radiated power quotas for agiven frequency band and/or carrier frequency and/or air interfacethereby may be observed.

In yet other embodiments of the invention, the aggregate radiated powercontroller is configured to control the ancillary terrestrial networkitself, i.e., the terrestrial infrastructure, to thereby reduce theradiated power by at least one radioterminal. In particular, in someembodiments, the aggregate radiated power controller is configured todiversity combine signals that are received from at least oneradioterminal by at least two ancillary terrestrial components and/or byan ancillary terrestrial component and at least one auxiliary antennasystem, to thereby reduce the radiated power by the at least oneradioterminal. The link margin and/or structural attenuation margin ofATN infrastructure components may thereby be increased.

More specifically, according to the Commission's analysis of theinterference potential to co-channel satellite systems by the ATN, thestructural attenuation margin provided by an ATN infrastructurecomponent on the return link(s) may be increased or maximized.Increasing or maximizing this parameter may have a direct impact on thefrequency reuse and/or the number of co-frequency communicationschannels allowed by the ATN. For a given maximum EIRP of an ATNradioterminal, the margin available by an infrastructure component on areturn link may be increased according to some embodiments of theinvention, by increasing the number of receive antenna elements on theATN tower(s) of the infrastructure component and/or by configuring atleast some of the receive antenna elements to operate on multiplespatially-orthogonal dimensions. This approach may yield aninfrastructure component able to provide ΦdB of structural attenuationmargin on forward links and ΨdB of structural attenuation margin onreturn links, where Ψ≧Φ. In the limit as Ψ→∞, the radioterminal EIRPapproaches zero and so does the interference potential to a co-frequencysatellite receiver. As such, the frequency reuse and/or the number ofco-frequency communications channels allowed by the ATN may beincreased.

FIG. 19 is a schematic diagram of systems and methods according toembodiments of the present invention, wherein the aggregate radiatedpower controller of FIG. 18 is configured to control an ancillaryterrestrial network of FIG. 19 to diversity combine signals that arereceived from at least one radioterminal by at least two ancillaryterrestrial components and/or by an ancillary terrestrial component andat least one auxiliary antenna system, to thereby reduce the radiatedpower by the at least one radioterminal. Moreover, according to otherembodiments of the present invention, embodiments of FIG. 19 may be usedto increase link margin in a satellite radioterminal system thatincludes an ATN, independent of an aggregate radiated power controller.

Referring now to FIG. 19, an ancillary terrestrial network 1850 includesa plurality of ancillary terrestrial components, shown in FIG. 19 asfirst and second ancillary terrestrial components 1900 a, 1900 b, eachof which communicates with at least one radioterminal 1930 over an areathat defines a respective cell 1920 a, 1920 b.

Still referring to FIG. 19, a tower of the first ATC 1900 a isconfigured with one or more transmit antennas and/or one or more receiveantennas. As stated earlier, at least some elements comprising thetransmitter and/or receiver antenna(s) of the infrastructure componentmay be operative in more than one spatial dimension. Moreover, a towerof the second ATC 1900 b may be configured with one or more transmitantennas and/or one or more receive antennas with at least some of theantenna elements thereof operative in more than one spatial dimension.The first ATC 1900 a and the second ATC 1900 b comprising theillustrative infrastructure component of FIG. 19, may be adjacent ATCs.Each ATC of an ensemble of ATCs that may comprise an infrastructurecomponent may have an associated cell 1920 a, 1920 b, that defines acell edge inside of which the ATC is configured to serve at least oneradioterminal 1930. A radioterminal that may be proximate to the cellboundaries/edges of at least two adjacent ATCs, as illustrated in FIG.19, may be served concurrently by at least two adjacent ATCs 1900 a,1900 b.

Accordingly, an infrastructure component comprising at least twoadjacent ATCs, as illustrated in FIG. 19, may be configured to utilizeone or more antenna elements per ATC to receive and process thetransmissions of the radioterminal, which can increase return linkrobustness and/or available return link margin. For example, as shown inFIG. 19, a base station processor 1930 of the second base station 1900 bmay be configured to forward transmissions that are received at thesecond base station 1900 b from radioterminal 1930 to a diversityreceiver 1902 at the first base station 1900 a via a terrestrial wiredand/or wireless link 1940. The diversity receiver also may be located,at least in part, outside the first base station 1900 a. The diversityreceiver 1902 may be used to combine the signals that are received atthe second base station 1900 b and the signals that are received at thebase station 1900 a from radioterminal 1930, to thereby increase thereturn link robustness and/or the available return link margin. As such,the available return link margin and/or structural attenuation marginprovided by the infrastructure component may be increased, facilitating,via closed-loop power control of the radioterminal by the infrastructurecomponent, a reduction in output power by the radioterminal, therebyreducing the potential of interference to a co-frequency system such asa co-frequency satellite system.

To increase or further increase the available return-link margin and/orreturn-link structural attenuation margin that may be provided by aninfrastructure component, according to other embodiments of the presentinvention, at least one additional auxiliary antenna system 1910 a-1910d may be disposed in the area/space between the cell edge and the basestation tower of at least one ATC comprising the infrastructurecomponent. FIG. 19 illustrates an infrastructure component configurationcomprising two auxiliary antenna systems per ATC of the infrastructurecomponent. However, greater or fewer auxiliary antenna systems 1910a-1910 d may be used.

Still referring to FIG. 19, a diversity receiver 1902 may be configuredto accept and process signals derived from the antenna systems of thefirst ATC 1900 a, auxiliary antenna system 1910 a, auxiliary antennasystem 1910 b, and from a base station processor 1930 associated withthe second ATC 1900 b. The signals derived from the auxiliary antennasystems 1910 a and/or 1910 b and/or from the antenna system of ATC tower1900 a may be sent to the diversity receiver 1902 via physicalconnection(s) and/or wirelessly. Similarly, the signals derived from theauxiliary antenna systems 1910 c and/or 1910 d and/or from the antennasystem of ATC tower 1900 b may be sent to the base station processor1930 via physical connection(s) and/or wirelessly.

The base station processor 1930 may also comprise a diversity receiver.The diversity receiver 1902 and/or base station processor 1930 may beconfigured to combine signals in accordance with any conventionaloptimum and/or sub-optimum performance index such as, for example,maximal ratio combining. The auxiliary antenna system(s) 1910 a-1910 dmay be configured to receive and/or transmit to/from radioterminals1930. Embodiments where the auxiliary antenna system(s) is/areconfigured to transmit to radioterminals may increase the availableforward-link margin and/or the forward-link structural attenuationmargin of the infrastructure component.

Accordingly, a first ancillary terrestrial component for a satelliteradioterminal system according to some embodiments of the presentinvention includes a subsystem, such as a base station tower 1900 a thatis configured to communicate terrestrially with a plurality aradioterminals 1930 over substantially the same frequency bands and/orair interfaces as the radioterminals communicate with a space-basedcomponent. A diversity receiver, such as diversity receiver 1902, isconfigured to diversity combine signals from a radiotelephone 1930 thatare received by the first ancillary terrestrial component 1900 a and/orby at least a second ancillary terrestrial component 1900 b, and/or byan auxiliary antenna system 1910. The auxiliary antenna system may belocated in the first cell 1920 a, such as auxiliary antenna systems 1910a, 1910 b, or may be included outside the cell, such as auxiliaryantenna systems 1910 c, 1910 d. These embodiments may also be used toincrease link margin, independent of control by an aggregate radiatedpower controller.

In conclusion, an ancillary terrestrial network can communicateterrestrially with a plurality of radioterminals over a plurality offrequency bands and/or a plurality of air interfaces, while theaggregate radiated power and/or power spectral density, over anypre-determined band of frequencies, may be limited to a predefinedmaximum.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A method of controlling a level of interference to a wirelessreceiver, the method comprising: determining a set of frequencies to beassigned to a wireless transmitter responsive to a power levelassociated with the wireless transmitter; and assigning the set offrequencies to the wireless transmitter; wherein determining comprisesincreasing a frequency distance between the set of frequencies and aband of frequencies used for reception by the wireless receiver as thepower level increases; and wherein determining further comprisesdecreasing a frequency distance between the set of frequencies and aband of frequencies used for reception by the wireless receiver as thepower level decreases.
 2. A method according to claim 1 whereinincreasing comprises monotonically increasing a frequency distancebetween the set of frequencies and the band of frequencies used forreception by the wireless receiver as the power level increases.
 3. Amethod according to claim 1 wherein decreasing comprises monotonicallydecreasing a frequency distance between the set of frequencies and aband of frequencies used for reception by the wireless receiver as thepower level decreases.
 4. A method according to claim 1 wherein the setof frequencies is in a satellite band of frequencies.
 5. A methodaccording to claim 1 wherein the wireless receiver is a wirelesstransceiver and wherein determining is further responsive to a detectionof a signal from the wireless transceiver.
 6. A method according toclaim 5 wherein the detection is performed by a base station serving thewireless transmitter.
 7. A system for controlling a level ofinterference to a wireless receiver, the system comprising: a wirelesstransmitter; and a controller that is configured to determine a set offrequencies to be assigned to a wireless transmitter responsive to apower level associated with the wireless transmitter; wherein thecontroller is further configured to increase a frequency distancebetween the set of frequencies and a band of frequencies used forreception by the wireless receiver as the power level increases; andwherein the controller is still further configured to decrease afrequency distance between the set of frequencies and a band offrequencies used for reception by the wireless receiver as the powerlevel decreases.
 8. A system according to claim 7 wherein the controlleris configured to monotonically increase a frequency distance between theset of frequencies and a band of frequencies used for reception by thewireless receiver as the power level increases.
 9. A system according toclaim 7 wherein the controller is configured to monotonically decrease afrequency distance between the set of frequencies and a band offrequencies used for reception by the wireless receiver as the powerlevel decreases.
 10. A system according to claim 7 wherein the set offrequencies is in a satellite band of frequencies.
 11. A systemaccording to claim 7 wherein the wireless receiver is a wirelesstransceiver and wherein the controller is further configured todetermine the set of frequencies responsive to a detection of a signalfrom the wireless transceiver.
 12. A system according to claim 11wherein the detection is performed by a base station serving thewireless transmitter.